Volume 1

The sector on a quadrant, or, a treatise containing the description and use of four several quadrants; two small ones and two great ones, each rendred many wayes, both general and particular. Each of them accomodated for dyalling; for the resolving of all proportions instrumentally; and for the ready finding the hour and azimuth universally in the equal limbe. Of great use to seamen and practioners in the mathematicks / Written by John Collins accountant philomath. Also an appendix touching reflected dyalling [by J. Lyon] From a glass placed at any reclination.

  • Collins, John, 1625-1683.
Date:
1659
Catalogue details

Licence: Public Domain Mark

Credit: The sector on a quadrant, or, a treatise containing the description and use of four several quadrants; two small ones and two great ones, each rendred many wayes, both general and particular. Each of them accomodated for dyalling; for the resolving of all proportions instrumentally; and for the ready finding the hour and azimuth universally in the equal limbe. Of great use to seamen and practioners in the mathematicks / Written by John Collins accountant philomath. Also an appendix touching reflected dyalling [by J. Lyon] From a glass placed at any reclination. Source: Wellcome Collection.

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    ^ Thel^e[criftiof%cfthe^(iddram. rprick ofFfcOiA the Center of the Qqadrant 66^ 29' the Complement ofc the Suns greateft Declination, which will find the Intcrfedion of the Tropick of Capricorn with the Meridian. Now to fit the Projedion to any particular Latitude; Out of the faid Line of Semi-tangents from the Center of the ^adrant, prick off the Latitude of the place, and it will find a pointin the Meridian Line, where the Horizon, orParalellofood of Alticudewillintcr- feft -^the Meridian ; this Point is called the Horizontal Point, and ■ferves for finding the Centers of all the Paralclls. To the Latitude of the place add each degree of Altitude'fucceffivc* ly till you have included the greateft Meridian Altitude; thefe com¬ pound Arks are fuch as being prickt fromlhe Center of the C^adrant out of the Line of Semi-tangents will find points in the Meridian Line, limiting the Semi-diameters of the paralclls of Alticudew Above the Horizon, and between the Circle that bounds the Pro- jedion falls a portion thereof called the Reverted Tail, which other- .wife would if it had not been there reverted, have excurred the limits of a Quadrant. To find the Interfedions for thofe.Paralclls of Altitude, fubftraft fucceffively each degree out of the Latitude of theplace, and the re¬ maining Arks prick from the Center out of the Line ofSemi-tangents: The ufe of this Tail being to find the hour ^nd Azimuth before or af¬ ter 6 in the Summer time only, it need be continued no further above the Horizon then the Ark of 2the Suns greateft Altitude at d, which at London Is iS^ I'd* •To finde the Centers ef the Faralells of Akitudh Thefe are to be difeovered by help of a Line of natural Tangents,, not numbred with the double Arks, whofe Radius muft be equal to the diftance of the Equator from the Center of the Quadrant, or which is all one to 9o<l of the Line of Semutangents; Out of this Line of Tangents prick off beyond the Center of the Quadrant the Complement of the Latitude, the diftance between the Paint thereby found, and the Horizontal Point is the Semi-diameter wherewith the Horizon is to be drawn. To find the Centers of the reft of the T^aralells. To the Complement of the Latitude add each degree of Altitude fuc-